1. Technical Field
This invention relates to the setting of blind rivets. More particularly, this invention relates to a blind rivet setting system in which a blind rivet is first set and then the correctness of the set of the rivet is verified.
2. Discussion
Rivets are widely used to firmly fasten together two or more components with little susceptibility to loosening and thus produce a tight joint at low cost.
The setting of the common rivet is accomplished when one end of the rivet is mechanically deformed to create a second head. The blind rivet is a special class of rivet that can be set without the need for mechanical deformation by a separate tool to create the second head. Special blind rivet setting tools are used for setting these types of rivets. Examples of such setting tools may be found in U.S. Pat. No. 3,713,321, issued on Jan. 30, 1973 to Gabriel for RIVET GUN, U.S. Pat. No. 3,828,603, issued on Aug. 13, 1974 to Scheffield et al. for RIVETING APPARATUS, and U.S. Pat. No. 4,263,801, issued on Apr. 28, 1981 to Gregory for HYDRAULIC RIVETER. These tools provide various approaches to setting rivets including setting by hydraulic and pneumatic power. A relatively sophisticated version of a blind rivet setting tool is disclosed in U.S. Pat. No. 4,744,238, issued on May 17, 1988, to Halbert for PNEUMATIC RIVET SETTING TOOL. This setting tool includes a rivet feed mechanism, a rivet magazine and sequencing controls providing cycle-through operation that utilizes pneumatic logic control.
A self-diagnosing blind rivet tool is disclosed in U.S. Pat. No. 4,754,643, issued on Jul. 5, 1988, to Weeks, Jr. et al. for METHOD AND APPARATUS FOR AUTOMATICALLY INSTALLING MANDREL RIVETS. This patent is directed to an automated and semi-automated rivet installation system that has the ability to diagnose selected tool conditions and to convey information on the conditions to the operator. Monitored conditions include the rivet placement within the tool, mechanism positions, and air pressure conditions.
One common shortcoming of prior art apparatus for the installation of blind rivets is the inability of the operator to gauge the correctness of the rivet set which, as the second head is created on the far side (or the blind side) of the elements being riveted, cannot be readily determined by observation or touch. In response to this need, it has been suggested that an electroacoustic transducer be used to convert the mechanical breaking of the mandrel at the conclusion of the setting process to an electric signal for determination of the correctness of the set. It has been further suggested that a strain gage be employed to sense the setting force of the rivet. These methods, however, provide the operator with limited set condition information. Consequently, the set condition of the rivet is assessable only in a marginal way.
Accordingly, there is still a need for a system by which a blind rivet may be first set and then the correctness of that set fully and reliably verified.